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E39 (1997 - 2003) The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

Getting the head cleaned/cut. Some warpage going on there and some coolant leaks. Waiting to hear if he found any cracks. Damn thing was a bear to pull off with all the crap attached to it.

Anyway, look at the scale and crap on top of these pistons. Shop guy does engines for the BMW Stealer in Charlotte and told me to stop burning 87 octane because it puts huge thick carbon deposits all over the place.

That was my reaction when I took the head off. Unbelievably disgusting. Don't think I've seen that since the carb days. No more crap gasoline for me. That avg $1.40 savings at the pump for an 8-10 gallon fillup costs more down the road.

how many miles were on your car? what made you take this job on? were there any noticeable issues?

166,500 and some change. Had to pull the head cause I couldn't find the source of a coolant leak after replacing the reservoir. Glad I did because the head was warped. Tech put the straight edge on there and pulled out his feeler gauge.... it slipped under there with ZERO resistance at the highest tolerable thickness gauge.

Getting it pressure tested and cut. Hopefully, he won't find any cracks, if he does and can fix it, fine. If he can't fix it, guess I'm saving up for a new head.

Went and got a wire brush attachment for my drill. Pretty fine wires, and if I don't put too much pressure on it, it shouldn't take off any appreciable metal. I'll put each cylinder at TDC before I do it and use a vacuum to suck out the mess.

Costco (also amazon dot com) sells a fiberoptic camera for $130 (similar to colonoscope that doctors use to look at bowel).
This camera has multiple purposes. it allows to inspect engine pistons etc. etc.

- Octane 87 does not do this.
- The common causes of carbon build-up on top of the pistons:
a. Mixture too rich
b. bad spark plugs create incomplete combustion
c. Oil consumption, in your case it could be a blocked CCV.

Costco (also amazon dot com) sells a fiberoptic camera for $130 (similar to colonoscope that doctors use to look at bowel).
This camera has multiple purposes. it allows to inspect engine pistons etc. etc.

- Octane 87 does not do this.
- The common causes of carbon build-up on top of the pistons:
a. Mixture too rich
b. bad spark plugs create incomplete combustion
c. Oil consumption, in your case it could be a blocked CCV.

Yeah, I figured the CCV had something to do with it, even though no usual CCV symptoms show. I don't know, this guy rebuilds engines and heads for Hendrick BMW in Charlotte. I'm going to heed his rant and never use 87 again in either E39.

Actually, despite my appreciation for people who use the recommended fuel in their cars, higher octane burns at a *lower* temperature than lower octane. Additionally, "proper" high-octane gas (i.e. gas that isn't ethanol blended to achieve the octane rating) gets there with higher levels of aromatic compounds that will increase carbon build-up if the car isn't built for it….and whether or not our cars are is up for debate, but they're not super-high compression engines.

Mine looked exactly the same when I pulled the head for a HG job. I suspected a coolant to cylinder 6 passage way leaking very small. The car never really overheated but would warm up with sprinted driving. I used roll-loc disc and sea foam, I then followed that with carb cleaner to get in the piston skirts with compressed air to blow it out. The compressed air helps a lot. Also after you will want to change your oil to get out any cleaner that seeped past the piston. 10k later and my car is great.

Actually, despite my appreciation for people who use the recommended fuel in their cars, higher octane burns at a *lower* temperature than lower octane. Additionally, "proper" high-octane gas (i.e. gas that isn't ethanol blended to achieve the octane rating) gets there with higher levels of aromatic compounds that will increase carbon build-up if the car isn't built for it….and whether or not our cars are is up for debate, but they're not super-high compression engines.

Just got back from dropping off my camshaft raceways and caps at the shop, and this is almost exactly what the owner told me word for word. He said that regardless of the octane ratings, the lower octane fuels produce more carbon which coats everything and.... this is important.... clogs the tiny passageways and sensors in the emissions sensors. Said that BMW engines were not built to withstand long time use of low octane "cheaper" fuel.

Either way, I'm gonna stop being cheap and start using higher grades of gasoline. For a 10 gal fillup, what am I saving by using 87? Maybe $2.50? $3.00? About $12-15.00/month? Is it worth it?

BTW, this old guy who does work for the dealer is a BMW schooled tech. Now, I know how we all feel about them, but either way..... I'm sure that using a better cleaner fuel will not hurt me.

The guy you're listening to appears to be badly misinformed about what an octane rating indicates.

However, you're welcome to put any fuel in your tank you want (it won't matter all that much either way, as it turns out) - so everyone is right (in a way).
- "The Gasoline FAQ" & top-tier gas stations (1)

See above. It's not the octane he's ranting about. And the CCV is getting replaced. Not going to bother testing it. I got the intake off, everything under there is getting replaced.

Getting the head cleaned/cut. Some warpage going on there and some coolant leaks. Waiting to hear if he found any cracks. Damn thing was a bear to pull off with all the crap attached to it.

Anyway, look at the scale and crap on top of these pistons. Shop guy does engines for the BMW Stealer in Charlotte and told me to stop burning 87 octane because it puts huge thick carbon deposits all over the place.

Yeeesh!!!

This post goes toward validating the argument AGAINST using low octane fuel vs recommended high octane. I always use 9X grade and some tried to argue in favor of 8X. Lower octane gas is less stable than high octane (under pressure). Pressure exerted on 8X by the pistons may prematurely ignite the 8X crap-gas (aka knocking). Our engines correct for the premature ignitions by changing the timing (prevents knocking). yet people STILL try to argue in favor of using crap-gas based on science that has ZERO to do with the reason BMWs require high octane fuel. BMWs have a high compression ratio as with most "performance" cars. Higher the compression the more likely 8X will ignite prematurely which is then corrected by throwing off the engine timing to compensate.

Crap-gas misfired timing WILL impact your fuel-air mixture. Which, in turn, CAN lead to more carbon buildup over time. As for the rest of the unrelated information, nothing promotes using 8X octane beyond people trying to drive an executive level car on a shoe string budget.

THANK YOU for this post as a picture says 1000 words. Not just because it validates my stand, more so because it is very educational for us all.

This post goes toward validating the areguement against using low octane fuel vs recommended high octane. I always use 9x grade and some tried to argue in favor of 8x. Lower octane gas is less stable than high octane (under pressure). Pressure exerted on 8x by the pistons may prematurely ignite the 8x crap-gas (aka knocking). Our engines correct for the premature ignitions by changing the timing (prevents knocking). Yet people still try to argue in favor of using crap-gas based on science that has zero to do with the reason bmws require high octane fuel. Bmws have a high compression ratio as with most "preformance" cars. Higher the compression the more likely 8x will ignite prematurely which is then corrected by throwing off the engine timing to compensate.

crap-gas misfired timing will impact your fuel-air mixture. which, in turn, can lead to more carbon buildup over time.

thank you for this post as a picture says 1000 words. Not just because it validates my stand, moreso because it is very educational for us all.

Over the years, I've read the entire canonical gasoline FAQ perhaps only a half-dozen times... and, well, I don't remember anything of the sort being said about that being any part of the difference between two fuels of differing octane ratings.

Still, your advisor is welcome to preach what he wants to whomever will believe - just as a religious mechanic is welcome to proselytize any particular religion to whomever will listen.

I'm not going to argue any further the point in this thread as you could read the gasoline FAQ yourself if you wanted to.

There's an entire thread devoted to that question over here:
- What are you actually saving/losing by using 87 vs 91 octane AKI (1)

The net cost savings is somewhere around a thousand dollars per hundred thousand miles - which is or isn't a lot depending on your perspective - but - it gets complicated because there are plenty of unknown factors - but that's all in the thread ... so there's no need to hash it out further here.

Tell ya what... my "advisor" has been pulling apart BMW engines for over 30 years, I would imagine he would have a pretty good idea what the results of different types of gasoline are on BMW engines. This thread was NOT started to rehash the ridiculous argument about 87 vs higher octane gas. If you would like to have that discussion, please take it to your octane thread. I have no intention of putting 87 octane in my BMW's anymore. If you choose to do so, that is your problem. I am not going to allow this thread to be hijacked like all the rest.

Tell ya what.... if you feel you know more about the effects of gasoline on BMW Engines, please give this man a call at his shop. I'm sure he'd be glad to discuss it with you.